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Chapter 20 EXAM @ Flashcards

1
Q

Define the cardiac cycle.

A

Period of time fr start of 1 heart beat to the start of next

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2
Q

Cardiac muscle tissue contracts on its own without neural or hormonal stimulation b/c of a phenomenon known as what?

A

Automaticity

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3
Q

What are the 3 components of the cardiac conducting system?

A

Sinoatrial Node
Atrioventricular node
Conducting cells

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4
Q

The SA node is located where?

A

Posterior wall of the R atrium nr entrance of the superior venacava

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5
Q

What is the location of the atrioventricular node?

A

Within the fl of the R atrium nr the opening of the coronary sinus

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6
Q

What pathways does a contractile stimulus follow to atrial muscle cells as an electrical impulse travels fr the SA node to the AV?

A

Internodal pathways

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7
Q

Which conducting cells are located in the ventricles?

A

AV bundle (bundle of his)
Bundle branches
Purkinje fibers

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8
Q

The gradual depolarization of the conducting cells of the SA node and the AV node is known as ___.

A

Prepotential

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9
Q

What causes pre potential of cardiac cells?

A

Slow influx of Na+ w/o a compensating outflow of K+

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10
Q

The ___ node generates action potentials at a rate of 80-100 per minute

A

SA

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11
Q

The AV node generates action potentials at what rate?

A

40-60/min

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12
Q

The SA node contains ___ ___ which set the heart rate.

A

Pacemaker cells

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13
Q

What connects the SA node to the AV node?

A

Internodal pathways

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14
Q

The connection between the AV node and the ___ ___ (aka ___ of ___), is normally the only elec connection between the atria and the ventricles.

A

AV Bundle

Bundle of his

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15
Q

Once an impulse enters the AV bundle, it travels to the interventricular septum and enters what part of the conduction sys?

A

Right and left bundle branches

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16
Q

What is an ectopic pacemaker?

A

Cells outside the conduction sys that set the HR that disrupt the the timing of the ventricular contraction

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17
Q

Which wave on the EKG represents the atrial depolarization?

A

P wave

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18
Q

The smaller ___ wave indicates ventricular depolarization.

A

T

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19
Q

The ___ interval extends fr the start of atrial depolarization to the start of the QRS complex

A

P-R

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20
Q

Extension of the P-R interval to longer than ____ can indicate damage to the conducting pathways or the AV node.

A

200 msec

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21
Q

The Q-T interval indicates what?

A

Time required for the ventricles to undergo a single cycle of depolarization and repolarization

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22
Q

What are some of the causes of long QT syndrome?

A 
Electrolyte disturbances
Meds
Conduction probs
Coronary ischemia 
Myocardial damage
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23
Q

An ____ is an irregularity in the normal rhythm or force of the heartbeat.

A

Arrhythmia

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24
Q

Serious arrhythmias may indicate what issues?

A

Damage to myocardium
Injuries to pacemakers or conduction pathways
Exposure to drugs
Abnormalities in electrolyte composition of
extracellular fluids

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25
What is the resting potential of a ventricular contractile cell?
-90mV
26
An action potential begins when the membrane of ventricular muscle reaches threshold at approx ____ mV.
-75 mV
27
What are the 3 steps in an action potential?
1. Rapid Depolarization 2. The Plateau 3. Repolarization
28
Fast sodium channels open during the rapid depolarization phase of an action potential. They are called fast channels b/c . . . .
They open quickly & remain open only for a few milliseconds
29
At what point in the action potential of a cardiac cell do sodium channels close?
As transmembrane potential reaches +30mV
30
Voltage gated Ca+ channels are known as slow Ca+ channels. Why?
B/c they open slowly & remain open for for a relatively long period
31
What causes the rapid depolarization phase of an action potential?
Na+ entry
32
How long does the rapid depolarization phase of an action potential last?
3-5 msec
33
What is the last thing that happens during the depolarization phase of the action potential?
Closure of voltage gated fast sodium channels
34
The plateau phase of the action potential begins with what?
Ca2+ entry
35
The plateau phase of the action potential lasts how long?
-175 msec
36
The plateau phase of the action potential ends with the closure of ___ ___ ___.
Slow calcium channels
37
What causes the repolarization phase of the action potential to start?
Loss of K+
38
What is the duration of the repolarization phase of an action potential?
75 msec
39
The repolarization phase of the action potential ends with what?
Closure of slow K channels
40
The period when a membrane will not respond to another stimulus for sometime after and action potential begins is know as what?
Refractory Period
41
What is the approx length of the refractory period in ventricular muscle?
200 msec
42
Define cardiac cycle.
The period between the start of one heart beat & the beginning of the next
43
What are the 2 phases of the cardiac?
Systole and Diastole
44
The phase in the cardiac cycle when a chamber contracts and pushes blood is known as what?
Systole
45
The phase in the cardiac cycle when the muscle relaxes and the chambers fill is known as ___.
Diastole
46
The brief period when all heart valves are closed, volumes in the ventricles do not change and ventricular pressures are rising is known as ___ ___.
Isovolumetric Contraction
47
What IDs the beginning point of ventricular ejection?
When pressure in ventricles exceeds that in arterial trunks, semilunar valves open and blood flows
48
During ventricular ejection each ventricle ejects 70-80 mL of blood. This is known as what?
Stroke volume
49
The amt of blood remaining in the ventricle when the semilunar valve closes is known as what?
End-systolic volume
50
The period when heart valves are closed, ventricular myocardium is relaxing and ventricular pressures are still higher than atrial pressures is known as what?
Isovolumetric relaxation
51
What happens to ventricular pressure during isovolumetric relaxation?
Ventricular pressure drops rapidly
52
Heart sound S1 marks what in the cardiac cycle?
Start of ventricular contraction when the AV valves close
53
When does the heart sound S2 occur?
At beginning of ventricular filling when semilunar valves close
54
What is occurring during heart sound S3?
Blood is flowing into the ventricles
55
What is occurring during heart sound S4?
Atrial contraction
56
What causes a heart murmur?
Probs w/papillary muscles or chordae tendineae causing heart valves to not close properly causing AV valve regurgitation
57
What is the term used to refer to the movements and forces generated during cardiac contractions?
Cardiodynamics
58
The amt of blood left in the ventricles at the end of ventricular diastole is called what?
End Diastolic Volume
59
The amt of blood left in the ventricles at the end of ventricular systole is called ___ -___ volume.
End-systolic
60
What is stroke volume?
Amt of blood pumped out of each ventricle during a single beat
61
What is the equation for Stroke Volume?
SV = End diastolic vol - End Systolic vol
62
The percentage of the End diastolic col represented by the Stroke Vol is called ___ ___.
Ejection Fraction
63
Define cardiac output.
Amt of blood pumped out of the L ventricle in one minute
64
What equation can we use to determine cardiac output?
CO = HR x SV
65
What are 2 factors affecting HR?
Autonomic Innervation | Hormones
66
What are 2 factors affecting stroke vol?
End diastolic vol | End systolic vol
67
The ANS and PNS innervate the heart by means of the nerve network known as the ___ ___.
Cardiac plexus
68
What is the location of the autonomic HQ for cardiac control?
Cardiac centers of the medulla oblongata
69
The ____ center controls sympathetic neurons that increase HR.
Cardioacceleratory
70
The ____ center controls parasympathetic neurons that slow HR.
Cardioinhibitory
71
Where do the cardioacceleratory and cardioinhibitory centers receive their info from?
Reflex pathways Higher centers PNS & SNS ctrs in Hypothalamus
72
Cardiac centers monitor baroreceptors and chemoreceptors innervated by what 2 nerves?
Glossopharyngeal (CN IX) | Vagus (CN X)
73
Cardiac centers respond to changes in ___ ___ reported by baroreceptors and to what 2 things from chemoreceptors?
Blood Pressure | Changes in arterial concentrations of dissolved O2 and CO2
74
What are 2 ways to increase HR through ANS innervation?
Decrease PNS activity | Increase SNS activity
75
How do SNS and PNS alter HR?
By changing ionic permeabilities of cells in the conducting sys.
76
Adjustments in HR in response to increases in venous return are caused by what reflex?
Arterial reflex of Bainbridge principle
77
What is the term given to the amt of blood returning to the heart by the veins?
Venous return
78
___, ___ and thyroid hormone increase HR by their effect on the SA node.
Epi | Norepi
79
____ ___ is the duration of ventricular diastole and is dependent upon what?
Filling time | HR
80
The degree of stretching in ventricular muscle cells during ventricular diastole is called ____.
Preload
81
Preload is directly proportional to what?
EDV
82
The idea that increasing EDV results in a corresponding increase in stroke vol is know as ___-___ principle.
Frank-Starling
83
___is the amt of force produced during a contraction at a given preload.
Contractility
84
Inotropy is a term that is related to what with regards to the heart?
Force of contraction (contractility)
85
SNS stimulation has a ____ inotropic effect where as PNS stimulation has a ____ inotropic effect.
Positive | Negative
86
The ___ is the amount of tension that the contracting ventricle must produce to force open the semilunar valve and eject blood.
Afterload
87
As afterload ____ stroke volume ____.
Increases | Decreases
88
An increase in venous return stretches nodal cells and produces what effect?
Increases HR
89
Stroke vol is the difference between what and what?
EDV and ESV
90
What 3 factors effect ESV?
Preload Degree of contractility Afterload
91
The difference between resting and maximal cardiac output is known as ___ ___.
Cardiac reserve

BI 212 (7 decks)

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